llvmbot wrote:

<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Tom Stellard (tstellar)

<details>
<summary>Changes</summary>

This change will cause clang and the other tools to statically link against the 
runtimes built in stage1.  This will make the built binaries more portable by 
eliminating dependencies on system libraries like libgcc and libstdc++.

---
Full diff: https://github.com/llvm/llvm-project/pull/127268.diff


1 Files Affected:

- (modified) clang/cmake/caches/Release.cmake (+16-4) 


``````````diff
diff --git a/clang/cmake/caches/Release.cmake b/clang/cmake/caches/Release.cmake
index 23e99493087ff..290e186baf6fe 100644
--- a/clang/cmake/caches/Release.cmake
+++ b/clang/cmake/caches/Release.cmake
@@ -48,10 +48,8 @@ set(CLANG_ENABLE_BOOTSTRAP ON CACHE BOOL "")
 
 set(STAGE1_PROJECTS "clang")
 
-# Building Flang on Windows requires compiler-rt, so we need to build it in
-# stage1.  compiler-rt is also required for building the Flang tests on
-# macOS.
-set(STAGE1_RUNTIMES "compiler-rt")
+# Build all runtimes so we can statically link them into the stage2 compiler.
+set(STAGE1_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind")
 
 if (LLVM_RELEASE_ENABLE_PGO)
   list(APPEND STAGE1_PROJECTS "lld")
@@ -90,9 +88,18 @@ else()
   set(CLANG_BOOTSTRAP_TARGETS ${LLVM_RELEASE_FINAL_STAGE_TARGETS} CACHE STRING 
"")
 endif()
 
+if (LLVM_RELEASE_ENABLE_LTO)
+  # Enable LTO for the runtimes.  We need to configure stage1 clang to default
+  # to using lld as the linker because the stage1 toolchain will be used to
+  # build and link the runtimes.
+  set(RUNTIMES_CMAKE_ARGS "-DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON" CACHE 
STRING "")
+  set(LLVM_ENABLE_LLD ON CACHE STRING "")
+endif()
+
 # Stage 1 Common Config
 set(LLVM_ENABLE_RUNTIMES ${STAGE1_RUNTIMES} CACHE STRING "")
 set(LLVM_ENABLE_PROJECTS ${STAGE1_PROJECTS} CACHE STRING "")
+set(LIBCXX_STATICALLY_LINK_ABI_IN_STATIC_LIBRARY ON CACHE STRING "")
 
 # stage2-instrumented and Final Stage Config:
 # Options that need to be set in both the instrumented stage (if we are doing
@@ -102,6 +109,11 @@ set_instrument_and_final_stage_var(LLVM_ENABLE_LTO 
"${LLVM_RELEASE_ENABLE_LTO}"
 if (LLVM_RELEASE_ENABLE_LTO)
   set_instrument_and_final_stage_var(LLVM_ENABLE_LLD "ON" BOOL)
 endif()
+set_instrument_and_final_stage_var(LLVM_ENABLE_LIBCXX "ON" BOOL)
+set_instrument_and_final_stage_var(LLVM_STATIC_LINK_CXX_STDLIB "ON" BOOL)
+set_instrument_and_final_stage_var(CMAKE_EXE_LINKER_FLAGS "-rtlib=compiler-rt 
--unwindlib=libunwind -static-libgcc" STRING)
+set_instrument_and_final_stage_var(CMAKE_SHARED_LINKER_FLAGS 
"-rtlib=compiler-rt --unwindlib=libunwind -static-libgcc" STRING)
+set_instrument_and_final_stage_var(CMAKE_MODULE_LINKER_FLAGS 
"-rtlib=compiler-rt --unwindlib=libunwind -static-libgcc" STRING)
 
 # Final Stage Config (stage2)
 set_final_stage_var(LLVM_ENABLE_RUNTIMES "${LLVM_RELEASE_ENABLE_RUNTIMES}" 
STRING)

``````````

</details>


https://github.com/llvm/llvm-project/pull/127268
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